This invention relates generally to laboratory tables and more particularly to honeycomb tabletops for use in supporting precision laboratory equipment.
Vibration isolation tables used for supporting highly sensitive equipment, such as optical and analytical devices, on a substantially vibration free surface are well known. Such systems generally include a tabletop comprising metallic upper and lower skins bonded to a honeycomb core and a connecting side wall. The upper skin of the tabletop typically contains a plurality of holes (usually drilled and tapped) which are used for securing equipment upon the tabletop surface. A honeycomb core with or without additional stiffening or damping components maintains a rigid separation between the skins and therefore the structural integrity of the top. These tabletops are commonly referred to as honeycomb tabletops. The tabletop is often supported by a vibration isolation system. An example of a vibration isolation system used with such a table would be the GIMBAL PISTON.TM., isolation system described in U.S. Pat. No. 4,360,184.
The honeycomb tabletop is an efficient structure for providing an array of tapped holes while also meeting the needs of flatness (e.g. .+-.0.005 in), magnetic permeability for optional use of magnetic chucks, and reasonable weight.
The drawbacks to drilling through and then tapping the rather thin skin (1/8" or 3/16" typically) in such a table are that the tapped hole is backed by a large cavity extending the full depth of the table. Further, in processing the top, cutting or tapping oils must be used, leaving residues in the table that are incompatible with clean optical surfaces, clean room processes, and the like. The alternative to tapping, that is, to press in an open or closed threaded insert, is less desirable because of the likelihood that the threaded insert will loosen after repeated screw installations.
In addition to the contaminants encountered in the processing of the tabletop, the tapped holes provide an opening through which liquid or other debris spilled upon the table surface may pass into the interior. Such spillage may pass laterally from one honeycomb cell to another and will obviously contaminate the interior of a table. The tabletop cannot be thoroughly cleaned, since the bonded table cannot be disassembled and contamination can spread via vapors and seepage to a clean room atmostphere.
Thus, there is a need for a honeycomb tabletop which is constructed in such a way that contaminants and spillage may be easily contained, and prevented from entering the interior of the tabletop. Cleanup will be made easier and there will be a greatly reduced risk of serious contamination.